chapter 18 - daltons law of partial pressures

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Chapter 18
Dalton’s Law of Partial Pressures
We all live in the ocean of air,
called the atmosphere.
Barometers and Standard
Atmospheric Pressure
Blizzard of 1978
The rapidly intensifying storm pulled bitter cold air from
the west across Ohio on winds of fifty to seventy miles an
hour. These conditions combined with heavy snow and
blowing of deep snow already on the ground to cause full
blizzard conditions all across Ohio.
• Atmospheric pressure of 28.28 inches at Cleveland was
the lowest pressure ever recorded in Ohio. This was also
the second lowest pressure not associated with a
hurricane recorded this century in the lower forty-eight
states.
• The arrival of the cold front and blizzard were
unmistakable. Temperatures fell thirty degrees in two
hours, winds increased to more than 70 miles an hour,
and blinding wind-blown snow filled the air.
• This blizzard caused the most complete disruption of
transportation ever known to Ohio. The Ohio National
Guard reported the immobilization of Ohio was
comparable to the results of a statewide nuclear attack.
•
A house in Wood County Ohio is
nearly buried.
Blizzard of 1978
Barometers and Standard
Atmospheric Pressure
• Standard atmospheric
pressure defined as the
pressure sufficient to support a
mercury column of 760mm high.
(units of mmHg, or torr).
• Another unit was introduced to
simplify things, the atmosphere
(1 atm = 760 mmHg).
• 1 atm = 760 mmHg = 760 torr =
101.3 kPa.
STP
standard temperature and pressure
Standard temperature
0°C or 273 K
Standard pressure
1 atm (or equivalent)
Dalton’s Law of Partial Pressure
• The total pressure of a mixture of gases is the sum of the
partial pressures of all the gases in the container.
• The contribution each gas makes to the total pressure of a
mixture of gases is known as the partial pressure of that
gas.
A
550 kPa
• Ptotal = PA + PB + PC
• Ptotal = 100 kPa + 250 kPa + 200 kPa = 550 kPa
Dalton’s Law of Partial Pressure
• What is the partial pressure of all the gas A in
the container with a total pressure of 900 kPa?
A
900 kPa
Gas A has a partial pressure of 164
kPa at a total pressure of 900 kPa.
Turn to the “Dalton’s Law of Partial
Pressures” sheet in your notebook.
Air is composed primarily of four gases: nitrogen (593.4 torr), argon
(7.098 torr), carbon dioxide (0.2508 torr), and oxygen. What is the
partial pressure of oxygen at standard atmospheric pressure?
• 593.4 torr + 7.098 torr + 0.2508 torr = 600.7488 torr
≈ 600.7 torr
• 760 torr – 600.7 torr = 159.3 torr ≈ 159 torr
Air is composed primarily of four gases: nitrogen
(593.4 torr), argon (7.098 torr), carbon dioxide (0.2508
torr), and oxygen. What percent of air is nitrogen?
593.4 torr
760 torr
x 100 = 78.1%
Air is composed primarily of four gases: nitrogen (593.4 torr),
argon (7.098 torr), carbon dioxide (0.2508 torr), and oxygen.
What is the partial pressure in kPa of argon gas at standard
atmospheric pressure?
7.098 torr
7.098 torr
torr
7.098 torr
kPa
torr
7.098 torr
101.3 kPa
760 torr
7.098 torr
101.3 kPa
760 torr
= 0.946 kPa
What would be the partial pressure of oxygen on top of a high
mountain where the air pressure is only 534 mm Hg?
Remember from the first problem that the partial pressure of
oxygen in air is 159 torr
159 torr
760 torr
=
X
534 torr
x = 112 torr
What percent less oxygen is dissolved into the blood
on top of the mountain as compared to sea level?
112 torr
159 torr
x 100 = 70.4%
100 – 70.4 = 29.6% less
Mount Everest
Endurance Training
Homework
 Dalton’s Law of Partial Pressures and Ideal
Gases Worksheet (due Tuesday).

chapter 18 - daltons law of partial pressures

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